JPH0778848A - Semiconductor device mounting method - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a bump bonding type semiconductor chip mounting method which does not require a step of remelting bumps and can remarkably improve productivity. [Structure and Effect] The semiconductor chip mounting method of the present invention is
It is characterized in that the deformation rate of the solder bumps is set to 10 μm / sec or less. It was found that good bonding strength can be obtained without adding a solder melting step. In a preferred aspect, the deformation rate of the solder bumps is 1 to 3 μm / sec or less. It has been found that this makes it possible to obtain a bonding strength almost comparable to that without adding a solder melting step. In a preferred embodiment, the strain rate is ε _t , the deformation resistance is σ, the proportional constant is k, the strain rate dependent exponent is m, and σ = k × ε.
It has been found that, when _t ^m is set, if the pressure welding is performed within a range of m of 0.3 or more, a bonding strength comparable to that of molten solder can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a semiconductor device,
The present invention relates to a method of mounting a flip-chip IC mounted face down.

[0002]

2. Description of the Related Art Conventionally, as a face-down mounting method of a flip chip IC, a solder bump formed on the surface of a connecting electrode of a semiconductor chip is directly pressure-contacted to a connecting electrode of a wiring board under a temperature condition below its melting point, and soldering is performed. A method is known in which a bump is plastically deformed and bonded to a connection electrode of a wiring board.

[0003]

However, in the above mounting method, the bonding strength of the solder bumps is inferior to that of the molten solder (solder reflow) method, so that there is a problem that a remelting step of the solder bumps is required after the bonding. It was The present invention has been made in view of the above problems, and an object thereof is to provide a bump bonding type semiconductor chip mounting method that does not require a step of remelting bumps and can significantly improve productivity as compared with the conventional method. I am trying.

[0004]

According to the method of mounting a semiconductor chip of the present invention, a solder bump formed on a surface of a connection electrode of a semiconductor chip is pressed against a connection electrode of a wiring board under a temperature condition below its melting point, In a method of mounting a semiconductor device in which a solder bump is plastically deformed to be alloy-bonded to a connection electrode of the wiring board, the solder bump has a deformation speed of 10 μm.
/ Sec or less.

In a preferred mode, the deformation rate of the solder bumps is 1 to 3 μm / sec or less. In a preferred aspect, the ratio of Sn to Pb of the solder bump is 30.
˜70 parts by weight to 70 to 30 parts by weight. In a preferred embodiment, the solder bump is a eutectic solder containing 61 to 65 wt% Sn.

In a preferred embodiment, the strain rate is ε _t , the deformation resistance is σ, the proportional constant is k, the strain rate dependent exponent is m, σ
= K × ε _t ^m, and the pressure welding is performed in a range where the strain rate dependence index m is 0.3 or more.

[0007]

The operation and effect of the invention The semiconductor chip mounting method of the first invention is characterized in that the deformation rate of the solder bumps is 10 μm / sec or less. It was found that good bonding strength can be obtained without adding a solder melting step.

In a preferred mode, the deformation rate of the solder bumps is 1 to 3 μm / sec or less. It has been found that this makes it possible to obtain a bonding strength almost comparable to that without adding a solder melting step. In a preferred embodiment, the ratio of Sn to Pb of the solder bump is 30 to 70 parts by weight to 70 to 30 parts by weight.

According to experiments, solder having this composition range is
Since the strain rate dependence index m described later becomes 0.3 or more,
It was found that good joint strength can be obtained as with eutectic solder. In a preferred embodiment, the solder bump contains Sn of 6
The eutectic solder contains 1 to 65 wt%.

Experiments have shown that solders in this composition range
Since the strain rate dependence index m described later becomes 0.3 or more,
It was found that good joint strength can be obtained as with eutectic solder. In a preferred embodiment, the strain rate is ε _t , the deformation resistance is σ, the proportional constant is k, the strain rate dependent exponent is m, and σ = k.
X ε _t ^m , the strain rate dependence index m is 0.
The pressure welding is performed within a range of 3 or more.

To explain this meaning, in order to bring the bonding strength of the solder bump close to the melting (alloy) level, it is necessary to realize good bonding not on a part of the bonding surface but on the entire surface. Between the strain rate ε _t and the deformation resistance σ, σ = k
The relationship of × ε _t ^m is established, and m is larger than ordinary metal in superplastic materials such as solder. The fact that m is large means the following. That is, since the deformation resistance σ of the portion where the strain rate ε _t is large due to a large external force locally is large, this portion is difficult to deform, while
Since the deformation resistance σ of the part where the strain rate ε _t is small due to the locally small external force is small, this part is easily deformed. That is, the small external force application site is easily deformed, and the large external force application site is not easily deformed.

If this is different from the above and if it is easy to deform both the small external force applying portion and the large external force applying portion, the strain rate ε _{t of the} portion to which a large external force is locally applied is ε _t.
Is large, the amount of deformation of this part is large, and the strain rate ε _{t of the} part where a small external force is locally applied is small, so the amount of deformation of this part is small. It deforms, and the amount of deformation of the portion to which the small external force is applied is insufficient, and in terms of the solder bump, the joining strength of that portion is insufficient. In particular, since the solder bump has a hemispherical shape and the external force is not uniformly applied, it is difficult to deform well over the entire bonding surface when m is small.

According to the experimental results, it has been found that the solder bump can obtain a bonding strength comparable to that of the molten solder if the strain rate dependence index m is 0.3 or more.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The device of this embodiment is a COG (Chi) device in which a semiconductor chip is mounted on a glass substrate (liquid crystal display device).
FIG. 1 shows a state in which the IC chip 2 is directly bonded on the glass substrate 1, FIG. 2 shows a state before the bonding, and FIG. 3 shows a main part of the IC chip 2 after the bonding.

An aluminum electrode 3 is formed as a chip-side connection electrode on the surface of the IC chip 2, and the surface thereof is covered with a passivation layer 4. A part of the aluminum electrode 3 is exposed, and a barrier metal 5 made of chromium or titanium is formed on the aluminum electrode 3 in this exposed part. Copper bumps 6 are arranged on the barrier metal 5, and solders 7 are arranged on the surfaces of the copper bumps 6.
As this solder 7, Pb-63Sn (eutectic solder)
Is used, and the melting point of this solder is 183 ° C. In the manufacturing process, after vapor deposition of the barrier metal 5, continuous plating of copper and solder is performed, and further, reflowing is performed at 250 ° C. in a non-diffraction atmosphere furnace so that the electrode tip portion has a hemispherical shape.

Glass substrate (wiring substrate) before bonding
1 is shown in FIG. 4 (plan view). A conductive pattern 10 is formed on the glass substrate 1 as a chip-side connection terminal. The conductive pattern 10 has a three-layer structure, and an ITO (indium tin oxide) layer 11, a nickel layer 12, and a gold layer 13 are sequentially laminated on a soda glass. This laminated structure is formed by vapor deposition of ITO / Ni / Au, similar to plating. Here, the gold layer 13 on the surface serves as an antioxidant for the ITO layer 11 and the nickel layer 12 as the wiring base material.

At the time of bonding, the glass substrate 1 is placed at a predetermined position, and the IC chip 2 is attached by the suction head.
Is transported to above the glass substrate 1 and is aligned. Then, the IC chip 2 is placed on the glass substrate 1. After that, a necessary load is applied to each bump from the back surface of the IC chip 2 (upper surface of FIGS. 1 and 2) with a heating head made of Dangsten (W), and the temperature of the heating head is set to 120 ° C.
Bring to ~ 175 ° C and hold for 10-30 seconds. That is, at a temperature lower than 183 ° C., which is the melting point of the solder 7, pressure is applied between the IC chip 2 and the glass substrate 1 to join the solder 7 while plastically deforming it.

At this time, since the heating temperature is not higher than the melting point of the solder 7, the solder 7 is not melted but is soft, and the joint is deformed and comes into surface contact. Further, when the solder 7 is joined while being plastically deformed under pressure, the surface of the solder 7 is advanced, and fresh solder is exposed to form a joint interface. Then, Au in the conductive pattern 10
(Gold) is almost diffused in the solder 7 near the joint,
Nickel also diffused in a small amount into the Sn particles at the interface E
It was confirmed by cross-sectional analysis by the DX analysis method.

Further, the connection area and the solder bump shape can be easily adjusted by adjusting the pressure applied by the heating head according to the number of terminals and the terminal size. The local heating may be performed by irradiating the bump portion with a laser instead of using the heating head. Here, the above-mentioned joining conditions will be described in detail.

The heating time (10 to 30 seconds) is a time sufficient for heat conduction from the heating head to the substrate side, and is an upper limit time for ensuring productivity. FIG. 5 shows changes in the bonding strength when the deformation speed (μm / sec) of the solder bump 7 is variously changed. However, the diameter of the solder bump 7 is about 250 μm, and its thickness (after deformation)
Is about 40 μm at maximum, and the thickness of copper bump 6 is about 30 at maximum.
μm.

A flip chip mounter (model name: flip chip mounter (custom-made product)) manufactured by Miss FA Co. was used as a joining device, and 44 solder bumps 7 were joined at the same time. The deformation speed is controlled by controlling the descending speed of the flip chip mounter, and the deformation speed is controlled at 40% for each deformation speed.
Tested once. As can be seen from FIG. 5, the bonding strength per bump electrode 7 is 80 g when the average deformation rate is 10 μm (strain rate ε _t conversion 10 ⁻¹ (1 / sec)), and 3 μm (strain rate ε _t Conversion 3 × 10 ^-1 (1 / se
The bonding strength per bump electrode 7 in c)) is 85 g.
1 μm (strain rate ε _t conversion × 10 ^-2 (1 / s
ec)), the bonding strength per bump electrode 7 is 88.
g weight was obtained.

Next, the same test was carried out by changing the composition of Sn and Pb of the solder bump 7 in the range of 30 to 70 parts by weight to 70 to 30 parts by weight. As a result, almost the same characteristics as in FIG. 5 were obtained. That is, when the average deformation rate is set to 10 μm or less, significantly better bonding strength is obtained as compared with the conventional deformation rate (30 to 50 μm / s), and when the average deformation rate is set to 1 to 3 μm, melting A joint strength almost equal to that of solder was achieved. In particular, if the solder bump is made of eutectic solder containing 61 to 65 wt% of Sn,
Since the strain rate dependence index m described later becomes large, good bonding strength was obtained.

Next, the strain rate ε _{t of} the eutectic solder described above
And the deformation resistance σ were investigated. The results are shown in FIG. For the test, a tensile tester manufactured by Shimadzu Corporation (model name: servo pulser (custom-made product)) was used, and the cross-sectional area of the plate-shaped test product was 20 mm ² . The strain rate ε _t is empirical formula σ =
It was determined by _k ε _t ^m , and σ was measured when ε _t was changed.

As can be seen from FIG. 6, the strain rate ε _t is 1
The strain rate dependence exponent m is 0.3 or more up to × 10 ⁻¹ (1 / sec), which is a region where the deformation resistance σ increases as the strain rate ε _t increases. Even if each part is different, uniform deformation is possible. Even with solder exhibiting superplasticity, the strain rate ε _t is 3 (1 /
sec) or more, especially 6 (1 / sec) or more, the deformation resistance σ does not increase despite the increase of the strain rate ε _t , and only this part locally deforms, and the entire plastic deformation occurs. Therefore, it can be estimated that the bonding strength is reduced.

In the above embodiment, the conductive pattern 10 (wiring material) is Au / Ni / ITO, but Au, Ni, S
Any material such as n, Ag, Ag-Pd, Ag-Pt, Cu that can be soldered may be used, and Pb-63S as the solder.
Solder having a composition other than n may be used, and the point is that it is a low melting point metal containing at least tin. Furthermore, although the solder 7 is provided on the copper bumps 6 (projection electrodes) in the above-described embodiment, it is not necessary to provide the projection electrodes in particular, and a method of supplying solder balls between the chip 2 and the substrate 1 may be used. The gold layer 13 can be omitted. Instead of the nickel layer 12, it is also possible to adopt a metal that can be alloyed with the solder bump 7.

[Brief description of drawings]

FIG. 1 is an enlarged view of a bonding portion (terminal portion) of this embodiment.

FIG. 2 is a diagram showing a state after bonding.

FIG. 3 is a diagram showing a terminal portion of an IC chip before bonding.

FIG. 4 is a diagram showing a terminal portion of a glass substrate before bonding.

FIG. 5 is a diagram showing a measurement result of a relationship between a deformation rate and a bonding strength.

FIG. 6 is a diagram showing measurement results of the relationship between strain rate and deformation resistance.

[Explanation of symbols]

 1 Glass substrate (wiring substrate) 2 Semiconductor chip 3 Aluminum electrode (semiconductor chip connection electrode) 7 Solder bump 10 Conductive pattern (wiring substrate connection electrode)

Claims (5)

[Claims] 1. A solder bump formed on the surface of a connection electrode of a semiconductor chip is pressed against a connection electrode of a wiring board under a temperature condition below its melting point, and the solder bump is plastically deformed to form a connection electrode of the wiring board. A method of mounting a semiconductor device, which comprises alloy bonding, characterized in that a deformation speed of the solder bump is 10 μm / sec or less. 2. The deformation rate of the solder bumps is 1 to 3 μm.
/ Sec or less, a method of mounting a semiconductor device. 3. The ratio of Sn to Pb of the solder bump is 30 to 70 parts by weight to 70 to 30 parts by weight.
A method for mounting a semiconductor device as described above. 4. The solder bump contains 61 to 65 wt% Sn.
% Eutectic solder. 5. In a preferred embodiment, the strain rate is ε _t , the deformation resistance is σ, the proportional constant is k, the strain rate dependent exponent is m, σ.
= A k × ε _t ^m, a mounting method of a semiconductor device according to claim 1, wherein the strain rate dependence exponent m is implementing said pressure within an amount of 0.3 or more.